The main objective is to develop suitable polymers as elastin substitutes in arteries and heart valves. First, the structure of elastin and its elasticity will be examined as a function of its water content. The methods to be employed are water absorption isotherm and heat capacity measurements supplemented by elasticity measurements. A major part of our studies will be concerned with measuring the glass point of elastin as a function of its water content. We found that below a critical water content elastin becomes hard and brittle. We propose that hardening of arteries might be associated with loss of water, accompanying lipid deposition. When we have an insight in the interaction of water with elastin in relation to its elasticity, we plan to measure the same properties for various synthetic polymers. Those polymers having similar properties are promising candidatss for tests in vivo. If they prove to be compatible with blood, they are probably suitable prosthetic materials for coronary arteries and heart valves.